In the normal course of wearing contact lenses, tear film and debris consisting of proteinaceous, oily, sebaceous, and related organic matter have a tendency to deposit and build up on lens surfaces. As part of the routine care regimen, contact lenses must be cleaned to remove these tear film deposits and debris. If these deposits are not properly removed, both the wettability and optical clarity of the lenses are substantially reduced causing discomfort for the wearer.
Further, contact lenses, especially those made from hydrophilic materials, must be continuously disinfected to kill harmful microorganisms that may be present or grow on the lenses. A number of methods for disinfecting contact lenses have been used such as the use of high temperatures, the use of oxidative chemicals, and the use of antimicrobial agents.
Conventionally, the cleaning of contact lenses is accomplished with one or both of two general classes of cleaners. Surfactant cleaners, generally known as "daily cleaners" because of their recommended daily use, are effective for the removal of most carbohydrate and lipid derived matter. However, they are not as effective for the removal of proteinaceous matter such as lysozyme. Typically, proteolytic enzymes derived from plant, animal, and microbial sources are used to remove the proteinaceous deposits. These "enzyme" cleaners are typically recommended for weekly use and are conventionally employed by dissolving enzyme tablets in suitable aqueous solutions.
The process of cleaning and disinfecting contact lenses typically involves several steps. The first steps typically comprise the cleaning phase whereby lenses are conventionally soaked in an enzyme cleaning solution at ambient temperature conditions, i.e., soaking for a period of up to 12 hours, to achieve effective removal of proteinaceous deposits, followed by rubbing the lens with a daily cleaner to further remove debris. After cleaning, the lenses are typically disinfected. Disinfection involves contacting the lenses with a solution containing an oxidative chemical (e.g. hydrogen peroxide) or an antimicrobial agent at ambient temperatures. Alternatively, disinfection may be accomplished by exposing the lenses to elevated temperatures for specified periods of time. This latter disinfection technique requires the use of a common electrical disinfecting apparatus.
Methods have been developed which can remove proteinaceous material from contact lenses while simultaneously disinfecting the lenses. For example, U.S. Pat. No. 4,614,549 discloses a single-step method of cleaning and disinfecting contact lenses in aqueous solutions of proteolytic enzymes at temperatures of between 60.degree. C. and 100.degree. C. Unfortunately, this method requires the use of an electrical disinfecting apparatus and elevated temperatures. Another example of a method for simultaneously cleaning and disinfecting contact lenses is described in U.S. Pat. No. Re. 32,672 which discloses a method wherein lenses are immersed in a solution containing peroxide and a peroxide active enzyme. However, this method requires an additional step of neutralization of the residual peroxide prior to inserting the lens into the eye.
In an effort to provide greater convenience, new regimens have been developed. For example, Bausch & Lomb offers a cleaning and disinfection system wherein lenses are simultaneous cleaned and disinfected by immersing the lens within ReNu.RTM. Multi-purpose Solution including a ReNu.RTM. enzymatic tablet (see for example U.S. Pat. No. 5,096,607 issued Mar. 17, 1992). This system provides the benefit of combined "daily" cleaning and disinfection in one solution, wherein the same solution may be directly used in combination with enzymatic cleaners, thus reducing the number of steps and components required for effective lens cleaning and disinfection.
Although the above-described Bausch & Lomb cleaning regimen offers significant convenience over prior art systems, further convenience is sought. More specifically, it is desired to provide a single solution capable of providing cleaning comparable with systems which utilize enzymatic cleaners.